1. Field of the Invention
This invention relates to novel inhibitors of p38 MAP kinase and related kinases, pharmaceutical compositions containing the inhibitors, and methods for preparing these inhibitors. They are useful for the treatment of inflammation, osteoarthritis, rheumatoid arthritis, psoriasis, Crohn's disease, inflammatory bowel disease, cancer, autoimmune diseases, and for the treatment of other cytokine-mediated diseases.
2. Description of the State of the Art
A number of chronic and acute inflammatory conditions have been associated with the overproduction of pro-inflammatory cytokines. Such cytokines include but are not limited to tumor necrosis factor alpha (TNF-α), interleukin 1 beta (IL-1β), interleukin 8 (IL-8) and interleukin 6 (IL-6). Rheumatoid Arthritis (RA) is a chronic disease where TNF-α and IL-1β are implicated in the onset of the diseases and in the progression of the bone and joint destruction seen with this debilitating condition. Recently approved therapeutic treatments for RA have included soluble TNF-α receptor (etanercept) and IL-1 receptor antagonist (anakinra). These treatments work by blocking the ability of their respective cytokines to bind to their natural receptors. Alternative methods to treat cytokine-mediated diseases are currently under investigation. One such method involves inhibition of the signaling pathway that regulates the synthesis and production of pro-inflammatory cytokines like p38.
P38 (also CSBP or RK) is a serine/threonine mitogen-activated protein kinase (MAPK) that has been shown to regulate pro-inflammatory cytokines. P38 was first identified as a kinase which became tyrosine phosphorylated in mouse monocytes following treatment with lipopolysaccharide (LPS). A link between p38 and the response of cells to cytokines was first established by Saklatvala J., et al., Cell, 78: 1039-1049 (1994), who showed that IL-1 activates a protein kinase cascade that results in the phosphorylation of the small heat shock protein, Hsp27, probably by mitogen-activated protein activated protein kinase 2 (MAPKAP kinase-2). Analysis of peptide sequences derived from the purified kinase indicated that it was related to the p38 MAPK activated by LPS in mouse monocytes, Han, J., et al., Science, 265: 808-811 (1994). At the same time it was shown that p38 MAPK was itself activated by an upstream kinase in response to a variety of cellular stresses, including exposure to UV radiation and osmotic shock, and the identity of the kinase that directly phosphorylates Hsp27 was confirmed as MAPKAP kinase-2, Rouse, J., et al., Cell, 78: 1027-1037 (1994). Subsequently, workers at SmithKline Beecham showed that p38 MAPK was the molecular target of a series of pyridinylimidazole compounds that inhibited the production of TNF from LPS-challenged human monocytes, Lee, J., et al., Nature, 372: 739-746. This was a key discovery and has led to the development of a number of selective inhibitors of p38 MAPK and the elucidation of its role in cytokine signaling.
It is now known that multiple forms of p38 MAPK (α, β, γ, δ), each encoded by a separate gene, form part of a kinase cascade involved in the response of cells to a variety of stimuli, including osmotic stress, UV light and cytokine mediated events. These four isoforms of p38 are thought to regulate different aspects of intracellular signaling. Its activation is part of a cascade of signaling events that lead to the synthesis and production of pro-inflammatory cytokines like TNF-α. P38 functions by phosphorylating downstream substrates that include other kinases and transcription factors. Agents that inhibit p38 kinase have been shown to block the production of cytokines including but not limited to TNF-α, IL-6, IL-8 and IL-1β in vitro and in vivo models Adams, J. L., et al., Progress in Medicinal Chemistry, 38: 1-60 (2001).
Peripheral blood monocytes (PBMCs) have been shown to express and secrete pro-inflammatory cytokines when stimulated with lipopolysaccharide (LPS) in vitro. P38 inhibitors efficiently block this effect when PBMCs are pretreated with such compounds prior to stimulation with LPS. Lee, J. C., et al., Int. J. Immunopharmacol., 10: 835-843 (1988). The efficacy of p38 inhibitors in animal models of inflammatory disease has prompted an investigation of the underlying mechanism(s) which could account for the effect of these inhibitors. The role of p38 in the response of cells to IL-1 and TNF has been investigated in a number of cells systems relevant to the inflammatory response using a pyridinyl imidazole inhibitor: endothelial cells and IL-8, Hashimoto, S., et al., J. Pharmacol. Exp. Ther., 293: 370-375 (2001), fibroblasts and IL-6/GM-CSF/PGE2 Beyaert, R., et al., EMBO J., 15: 1914-1923 (1996), neutrophils and IL-8 Albanyan, E. A., et al., Infect. Immun., 68: 2053-2060 (2000) macrophages and IL-1 Caivano, M. and Cohen, P., J. Immunol, 164: 3018-3025 (2000), and smooth muscle cells and RANTES Maruoka, S., et al., Am. J. Respir. Crit. Care Med., 161: 659-668 (1999). The destructive effects of many disease states are caused by the over production of pro-inflammatory cytokines. The ability of p38 inhibitors to regulate this overproduction makes them excellent candidates for disease modifying agents.
Inhibitors of p38 are active in a variety of widely recognized disease models and show positive effects in a number of standard animal models of inflammation including rat collagen-induced arthritis, Jackson, J. R., et al., J. Pharmacol. Exp. Ther., 284: 687-692 (1998); rat adjuvant-induced arthritis, Badger, A. M., et al., Arthritis Rheum., 43: 175-183 (2000); Badger, A. M., et al., J. Pharmacol. Exp. Ther., 279: 1453-1461 (1996); and carrageenan-induced paw edema in the mouse, Nishikori, T., et al., Eur. J. Pharm., 451: 327-333 (2002). Molecules that block p38's function have been shown to be effective in inhibiting bone resorption, inflammation, and other immune and inflammation-based pathologies in these animal models. Thus, a safe and effective p38 inhibitor would provide a means to treat debilitating diseases that can be regulated by modulation of p38 signaling like, but not limited to, RA.
P38 inhibitors are well known to those skilled in the art. Reviews of early inhibitors have helped establish the structure activity relationships important for enhanced activity both in vitro and in vivo. See, Salituro, E. G., et al., Current Medicinal Chemistry, 6: 807-823 (1999) and Foster, M. L., et al., Drug News Perspect., 13: 488-497 (2000). More contemporary reviews have focused on the structural diversity of new inhibitors being explored as p38 inhibitors Boehm, J. D. and Adams, J. L., Exp. Opin. Ther. Patents, 10: 25-37 (2000). This invention describes a novel series of substituted 2-aza-[4.3.0]-bicyclic heteroaromatic compounds as p38 inhibitors that are useful for the treatment of inflammation, osteoarthritis, rheumatoid arthritis, cancer, auto-immune diseases, and for the treatment of other cytokine mediated diseases.